Conclusions
In general the outcome of the game justified itself - the game was fun for us and kids. They could learn something outside and in different environment; they got new information about their hometown, reinforced the acquired knowledge through practical tasks.
The kids were surprisingly good in teamwork and finding their way in difficult situations (asking the way and help from strangers in the streets and doing it politely) without the teacher.
As to the negative sides - using mobiles was a bit complicated (sending pictures took too much time).
The kids were extremely fond of the game and they are interested in playing the game in different environments and more often than just once.
In the future the puppet master should be given more responsibilities in leading the game (giving hints, finding answers from the Internet etc.)